Blending apparatus for solids



Dec. 3, 1968 s. A. MGKAY 3,414,164

BLENDING APPARATUS FOR SOLIDS Filed March 6, 1967 [.VVENTOR. STEPHEN A M KAY PATENT AGENT United States Patent 3,414,164 BLENDING APPARATUS FOR SOLIDS Stephen A. McKay, St. Bruno, Quebec, Canada, assignor to Electric Reduction Company of Canada, Ltd., Toronto (Islington), Ontario, Canada Filed Mar. 6, 1967, Ser. No. 620,991 9 Claims. (Cl. 222-64) ABSTRACT OF THE DISCLOSURE A blendin apparatus for particulate material, consisting of a vertical container divided internally by vertical partitions of different heights into several sector-like compartments of different heights. The compartments empty at the bottom into a common mixing chamber with a single outlet. Particulate material is delivered continuously to the highest compartment, which fills up and overflows into an adjacent compartment, which fills and overflows into the next, and so on.

This invention relates to a blending apparatus adapted to receive continuously a particulate product of which the properties are not uniform on a time basis, and to deliver the particulate product as a mixture of product received at different periods, thereby improving its uniformity. For example, a blending apparatus of the type to which this invention is directed could be constructed such that the particulate product being delivered therefrom at a given point in time would consist of a mixture of particulate product received by the apparatus at points 3 mins., *6 mins., 9 mins., and 12 mins. prior to said point in time. As will readily be appreciated, blending of this nature will result in a significantly more uniform product, and the increase in uniformity will be mathematically calculable.

It is an object of this invention to provide a blending apparatus which will increase the uniformity of a nonuniform particulate product delivered from a continuous processing unit.

Accordingly, this invention provides blending apparatus for par-ticulate material, comprising: a first compartment and a second compartment separated by a substantially vertical partition, said partition having an upper edge over which particulate material can overflow from said second compartment into said first compartment, means for introducing particulate material from above into said second compartment, both said compartments debouching at the bottom into a common mixing chamber, an outlet from said common mixing chamber, detecting means for detecting the level of particulate material in said first compartment, and regulating means controlled by said detecting means for regulating the rate of outflow of particulate material through said outlet so as to maintain the general level of particulate material in the first compartment substantially at a fixed location, said fixed location being below said upper edge.

One embodiment of this invention is shown in the accompanying drawing, in which like numerals refer to like parts throughout the several views, and in which:

FIGURE 1 is a perspective view of a blending apparatus, a portion of which has been assumed transparent for convenience in showing the inner structure thereof;

FIGURE 2 is a perspective view similar to FIGURE 1, but turned through 90", showing the flow and distribution of particulate material through the blending apparatus;

FIGURE 3 is a hypothetical view of the inside wall of the blending apparatus shown in FIGURES 1 and 2, the inside wall having been slit and opened out flat.

In FIGURE 1, a blending apparatus shown generally 3,414,164 Patented Dec. 3, 1968 at 10 is seen to consist of a cylindrical housing 11 of which the top end 12 is open, and of which the bottom end 13 is connected to and communicates with a funnelshaped mixing chamber 14. The mixing chamber 14 converges downwardly to an outlet 15. For convenience of illustration, the cylindrical housing 11 has been shown as transparent, in order to permit a clear description of the internal portion of the blending apparatus 10.

Located within the cylindrical housing 11, and extending radially outwardly from the centre line 17 thereof, are a first partition 20, a second partition 21, a third partition 22, and a septeum 23. Except for its shape, the septum 23 is not different in construction from the partition 22, and .a septum 23. Except for its shape, the clature has been adopted because the septum 23 does not function in the same way as do the partitions 20, 21 and 22.

The three partitions and the septum are at right angles with respect to each other, and thus divide the interior of the cylindrical housing 11 into four quadrants. The partitions and the septum extend downwardly only as far as the bottom 13 of the cylindrical housing 11. In the following description, the four quadrants will be referred to as compartments: a first compartment 25 being defined between the first partition 20 and the septum 23; a second compartment 26 being defined between the first partition 20 and the second partition 21; :a third compartment 27 being defined between the second partition 21 and the third partition 22; and a fourth compartment 28 being defined between the third partition 22 and the septum 23.

All of the compartments 25, 26, 27 and 28 debouch at the bottom into the mixing chamber 14 which is common to all of the compartments.

The first partition 20 has an upper edge 30 over which particulate material can overflow from the second compartment 26 into the first compartment 25 when the second compartment 26 has been filled to overflowing. Likewise, the second partition 21 has an upper edge 31 over which particulate material can overflow from the third compartment 27 into the sec-ond compartment 26 when the third compartment 27 has been filled to overflowing. In the same manner, the partition 22 has an upper edge 32 over which particulate material can overflow from the fourth compartment 28 into the third compartment 27 when the fourth compartment 28 has been filled to overflowing. It will be noted that the elevation of the upper edges 30, 31 and 32 of the partitions 20, 21 and 22 progressively increases from the first to the third partition. In the preferred embodiment, the upper edges of the partitions differ in height by substantially equal increments. The septum 23 extends above the level of the upper edge 32 of the third partition 22.

In FIGURE 1, an imaginary horizontal line 34 has been dotted in on the septum 23 at a point which is lower than the upper edge 30 of the partition 20 by a distance substantially equal to the increment between adjacent partitions. Bracketing the line 34 are a high level switch 35 and a low level switch 36, the former above, and the latter below, the line 34. The switches 35 and 36 constitute detecting means for detecting the level of particulate material in the first compartment 25, and can be of any conventional kind. Those familiar with the field will appreciate that other well-known devices could be used in place of the switches 35 and 36 for detecting the level in compartment 25. The switches 35 and 36 control regulating means 38 for regulating the rate of outflow of particulate material through the outlet 15, so as to maintain the general level of particulate material in the first compartment 25 substantially at the line 34. Because such controlling means are familiar to those versed in the art,

all that has been shown in FIGURES 1 and 2 is a representative device consisting essentially of a box 39 fixed with respect to the blending apparatus 11 and an extensible and retractable tongue 40, adapted to close or open the outlet 15 according as the switches 35 and 36 call for a lesser or a greater outflow of particulate material. It could be of advantage to use an iris-type closure device, operating on the principle of a camera shutter, opening and closing concentrically with the outlet 15. It would also be possible to use capacitative and other level detectors which can give a proportional signal which would enable continuous control to be applied to the outlet rate.

As mentioned earlier, the blending apparatus of this invention is adapted for use with a processing unit which continuously delivers a product of which the characteris' tics (physical, chemical, etc.) vary from time to time. For example, a given product from a given continuous process may be delivered for 5 mins. with a moisture content of about 11%, followed by 2 mins. with a moisture content of about 12 /2%, followed by 4 mins. with a moisture content of about etc. The preferred embodiment of the blending apparatus of this invention is adapted to mix together, and deliver as a continuous outflow, product produced W mins. ago, product produced X mins. ago, product produced Y mins. ago, and product produced Z mins. ago. Preferably, W, X, Y, and Z differ by equal increments. For example, X, Y, Z, and W may be 2, 4, 6 and 8 (minutes) respectively.

Turning now to FIGURE 1, a chute 42 represents the delivery end of the continuous process of which the product is to be blended by the blending apparatus of the present invention. The chute 42 delivers the product continuously into the fourth compartment 28. At start-up, the blending apparatus is, of course, empty. The product falls from the chute 42 through the compartment 28 and collects in the mixing chamber 14 until the latter is filled. Since there is no particulate material in the first chamber 25, the switches 35 and 36 will be calling for no outflow, and the tongue 49 will be in the closed position shown in FIGURE 1. As soon as the level of particulate material in the mixing chamber 14 has risen to block the bottom of the fourth compartment 28, the compartment 28 will begin to fill up until it has reached the level of the upper edge 32 of the third partition 22. At this point, the particulate material, still flowing out of the chute 42, will overflow into the third compartment 27, which will fill up in the same way, and then overflow into the second compartment 26, which in turn will fill up and overflow into the first compartment 25. The flow of particulate material is depicted in FIGURE 2, in which the partitions -22 and the septum 23 have been turned counterclockwise through 90, for purposes of illustration.

When the level of particulate material in the first chamber 25 has risen to the point where it is detected by the high level switch 35, the latter will instruct the regulating means 38 to withdraw the tongue 40 from sealing relation with the outlet 15, thus permitting particulate material to flow out of the mixing chamber 14. The outlet 15 from the bottom of the mixing chamber 14 prefer- .ably has a slightly greater capacity than the inlet feed rate from the chute 42, such that upon withdrawal of the tongue 40, the level of particulate material in the first compartment 25 will begin slowly to drop. When the level has dropped to the low level switch 36, the regulating means 38 is instructed to extend the tongue 40 once more into sealing relation with the outlet 15.

When the blending apparatus of this invention is under continuous operation, with the outlet rate being the same as or slightly greater than the inlet feed rate from the feed chute 42, the rate at which particulate material passes from each compartment into the mixing chamber 14 will be substantially the same (due to the fact that their crosssectional areas are equal), and will be approximately /4 of the discharge rate. It could not be otherwise, since the rate at which material passes out of the mixing chamber 14 must be exactly the same as the rate at which particulate material passes into the chamber 14 from all four sources. If the discharge rate is adjusted so as to be as nearly as possible equal to the entry rate from chute 42, it will be appreciated that the fourth compartment 28 will absorb particulate material at a rate which is A that of the feed from the feed chute 42. In consequence, three parts out of every four falling into the compartment 28 must overflow into the third compartment 27. By the same taken, two parts out of every three overflowing into the third compartment 27 must overflow into the second compartment 26. Likewise, of these two parts overflowing into the second compartment 26, one must overflow into the first compartment 25. It will furthermore be appreciated that this quadripartite distribution of the infeed of particulate material is in no way dependent upon the fact that the heights of the three partitions differ by equal increments. The equal height increments merely ensure that the time increments between the four components of the outflow from the blender (i.e. the W, X, Y and Z mentioned above) will be substantially the same, provided that the feed rate from the chute 42 is constant. Substantially equal quantity distribution as between the four compartments will be obtained so long as adjacent partitions differ in height by a sufiicient distance that the angle of repose of the particulate material does not bring the particulate material in any given compartment up to or beyond the upper edge of the partition over which particulate material is flowing into that given compartment; that is, so long as particulate material actually falls downwardly from one compartment to the next. Another way of expressing this is to say that the particulate material undergoes free fall along the whole of the upper edge of a partition dividing adjacent compartments.

In FIGURE 3, the laminae A, B, C, etc., represent particulate material that has flowed into the blending apparatus from the feed chute 42 in sequential periods of 2 minutes duration each. Two minutes is chosen for the sake of illustration only. In actual fact, there will be no recognizable interfaces between the diiferent laminae. The feed chute 42 is just completing the most recent period of 2 minutes duration, and the particulate material that has flowed into the blending apparatus during this period is designated as A. The particulate material that entered the blending apparatus in the previous 2 minute period is designated B, and so on. It will be noted that at the present time the material flowing out of the outlet 15 consists of material from laminae E, F, G, and H. Ideally, each of these portions makes up A of the outflow.

While the embodiment shown in the drawing and described above comprises four compartments, it will be appreciated that the basic aim of this invention, that of mixing together product produced at different points of time, is achieved solong as there are at least two compartments, one of which is filled from above with particulate material and overflows into the other, both compartments debouching into a common mixing chamber. Conversely, it may be desirable to provide more compartments than four, the number selected being appropriate to the variability of the process being blended.

As mentioned above, the fact that the heights of the partitions differ by equal increments has the result that the mixed product flowing out of the outlet 15 is made up of components produced at points in time separated by substantially equal periods, provided that the flow from the chute 42 is at a constant rate. Regardless of whether the flow rate from the chute 42 is constant or irregular, however, the components contributing to the mixed product at the outlet 15 will be separated by substantially equal quantities of material. For example, in FIGURE 3, the E component flowing out of compartment 25 and the F component flowing out of compartment 26 are separated (on a mass or weight basis) by the equivalent of all the material of any one lamina in all four compartments.

If the heights of the partitions differ by unequal increments, the weight increments between the components of the final outflow at will vary accordingly (as will the time increments, if the feed rate from the chute 42 is constant).

It is conceivable that satisfactory mixing could be obtained if the incremental height differences between adjacent partitions were not sufficiently great to ensure that particulate material would fall downwardly from one compartment into the adjacent one along the whole of the upper edge of the dividing partition. Provided the surface of the particulate material sloped downwardly from an upstream to a downstream compartment, some mixing would take place in the mixing chamber 14, although the partial or total lack of the falls effect over the partitions would likely introduce randomness and variability into the blending.

In the preferred embodiment, each of the compartments has approximately the same cross-sectional area, but this equality is not considered an essential limitation. Mixing will still take place if one compartment is twice or thrice the area of another, and the contribution of each compartment to the final mixed, delivered product will be approximately proportional to its area. The depth of the material in each compartment will also have some effect upon its contribution to the final product.

In actual practise, it will likely be desirable to provide a lid or cover for the apparatus described above. Such has not been shown in the drawings, however, as it forms no part of this invention.

While a preferred embodiment of this invention has been disclosed herein, those skilled in the art will appreciate that changes and modifications may be made therein without departing from the spirit and scope of this invention as defined in the appended claims.

What I claim as my invention is:

1. Blending apparatus for particulate material, comprising:

a first compartment and a second compartment separated by a substantially vertical partition, said partition having an upper edge over which particulate material can overflow from said second compartment into said first compartment,

means for introducing particulate material from above into said second compartment,

both said compartments debouching at the bottom into a common mixing chamber,

an outlet from said common mixing chamber,

detecting means for detecting the level of particulate material in said first compartment,

and regulating means controlled by said detecting means for regulating the rate of outflow of particulate material through said outlet so as to maintain the general level of particulate material in the first compartment substantially at a fixed location, said fixed location being below said upper edge.

2. Blending apparatus as claimed in claim 1, in which said means for introducing particulate material comprises:

a third compartment separated from said second compartment by a further substantially vertical partition,

said further partition having an upper edge over which particulate material can overflow from said third compartment into said second compartment, the upper edge of said further partition being higher than that of said first-mentioned partition,

the third compartment debouching at the bottom into said common mixing chamber,

and means for introducing particulate material from above into said third compartment.

3. Blending apparatus as claimed in claim 2, in which said last-mentioned means comprises:

a fourth compartment separated from said third compartment by a still further substantially vertical partition, said still further partition having an upper edge over which particulate material can overflow from said fourth compartment into said third compartment, the upper edge of said still further partition being higher than that of said further partition,

the fourth compartment debouching at the bottom into said common mixing chamber,

and means for introducing particulate material from above into said fourth compartment.

4. Blending apparatus as claimed in claim 1, in which the cross-sectional areas of the first and second compartments are substantially equal.

5. Blending apparatus as claimed in claim 3, in which the first, second, third and fourth compartments are defined as quadrants within a substantially cylindrical housing, said partitions being radially disposed within said housing, the tfirst and fourth compartments being separated by a septum which extends above the height of the upper edge of said still further partition.

6. Blending apparatus as claimed in claim 1, in which said detecting means comprises a high level switch and a low level switch located the former above the latter on a wall of the first compartment remote from said partition.

7. Blending apparatus as claimed in claim 5, in which the upper edges of the partitions are horizontal and differ in height by substantially equal increments.

8. Blending apparatus as claimed in claim 7, in which the particulate material undergoes free fall along the whole of the upper edge of each partition.

9. Blending apparatus as claimed in claim 8, in which said detecting means comprises a high level switch and a low level switch located the former above the latter on a wall of the first compartment remote from said partition, said switches bracketing a point which is lower than the upper edge of said partition by a distance equal to the increment between adjacent partitions.

References Cited UNITED STATES PATENTS 1,489,933 8 4/1924 Hale 22264 X 2,642,206 6 1953 Reed 222 X 2,994,460 8/ 1961 Matthews 2221 45 FOREIGN PATENTS 228,937 10/ 1959 Australia.

ROBERT B. REEVES, Primary Examiner.

F. R. HANDREN, Assistant Examiner. 

